Charterers' Liabilities and Bunkers & The Quality of Bunkers

1. Charterers' Liabilities and Bunkers&The Quality of Bunkers § 正蒙養而裨後學---傳承----§ 主講人: 陳麒太 on Dec.3, 2009

2. Introduction Neither shipowners nor charterers like to receive poor quality bunkers. This can lead to a number of problems, which include: - damage to main or auxiliary engines;- finding terminals willing to receive de-bunkered fuel;- co-ordinating and bearing the costs associated with diverting a vessel for off-spec bunkers discharge;- co-ordinating and bearing the costs of providing new bunkers to a vessel; - reducing speed to accommodate the use of off-spec bunkers; - co-ordinating and bearing the cost of lost time, i.e., off-hire. These problems can lead to disputes between shipowners and charterers. The objective of this article is to present case study examples of incidents, explain how disputes can arise and provide some guidance as to how shipowners and charterers can protect their interests.

7. 重油規格之特性 • 比重: 通俗性的基本比較方式: 比重小: 好油，比重大: 劣質油 • 黏度: 1. 油滴的燃燒: 油氣。 • 2. 黏度與燃燒性的關係: 噴油的霧化程度。 • 殘留碳: 成分愈多，燃燒性愈差。 結果: 造成火焰延長，汽缸燃燒之 高溫帶延伸，導致活塞冠吹溝、易刮傷襯套內壁、或異常磨耗及龜裂。 • 觸媒為粉粒: 主機故障之熱門題目。使保養費用急遽增加的頭號禍魁。 • 親和性: 重油因製程不同。且游品在混配後，因本身碳氫化合物之不安定性，易產生膠質沉澱物於艙底，隨儲存的時間愈久，現象愈明顯，造成泵油不易。

8. 加油時應注意事項: • 加油樣品之採樣及封存 • 觸媒微粉粒之檢查要領 • 加油時儘量避免新舊重油混存

9. 討論: ---End---

10. Pressure Surge 主講人: 陳麒太 on Dec.3, 2009

11. 1. Introduction • If the pressure surge in the pipeline results in pressure or displacement stresses in excess of the strength of the piping or its components, there may be a rupture leading to an extensive spill of oil. • A pressure surge is generated in a pipeline system when there is an abrupt change in the rate of flow of liquid in the line. In tanker operations it is most likely to occur as a result of one of the following during loading: • Closure of an automatic shut down valve. • Slamming shut of a shore non-return valve. • Slamming shut of butterfly type valve. • Rapid closure of a power operated valve.

12. 2. Generation of Pressure Surge When a pump is used to convey liquid from a feed tank down a pipeline and through a valve into a receiving tank, the pressure at any point in the system while the liquid is flowing has three components: • Pressure on the surface of the liquid in the feed tank. In a tank with its ullage space communicating to atmosphere this pressure is that of the atmosphere. • Hydrostatic pressure at the point in the system in question. • Pressure generated by the pump. This is highest at the pump outlet, decreasing commensurately with friction along the line downstream of the pump and through the valve to the receiving tank.

13. 3. Assessment of Pressure Surges • Effective Closure Time of the Valve • Derivation of Total Pressure in the System • Overall System Design

14. Effective Closure Time of the Valve • In order to determine whether a serious pressure surge is likely to occur in a pipeline system the first step is to compare the time taken by the valve to close with the pipeline period. • The effective valve closure time, i.e. the period during which the rate of flow is in fact decreasing rapidly, is usually significantly less than the total time of movement of the valve spindle. It depends upon the design of the valve, which determines the relationship between valve port closure of the last quarter or less of the valve port area. • If the effective valve closure time is less than, or equal to, the pipeline period, the system is liable to serious pressure surges. Surges of reduced, but still significantly, magnitude can be expected when the effective valve closure time is greater than the pipeline period, but they become negligible when the effective valve closure period is several times greater than the pipeline period.

15. Derivation of Total Pressure in the System • In the normal type of ship/shore system handling petroleum liquids, which the shore tank communicates to the atmosphere, the maximum pressure applied across the pipe wall at any point during a pressure surge is the sum of hydrostatic pressure, the outlet pressure of the pump at zero throughput and the surge pressure. The first two of these pressure are usually known.

16. Overall System Design • In the Chapter the simple case of a single pipeline has been considered. In practice the design of more complex system may need to be taken into account. For example, the combined effects of valves in parallel or in series have to be examined. In some cases the surge effect may be increased; this can occur with two lines in parallel if closure of the valve in one line increases the flow in the other line before this line in its turn is shut down. On the other hand, correct operation of valves in series in a line can minimize surge pressure.

17. 4. Reduction of Pressure Surge Hazard • Reduce the linear valve rate, i.e. the rate of transfer of cargo, to a value which makes the likely surge pressure tolerable. • Increase the effective valve closure time. In very general terms total closure times should be of the order of 30 seconds, and preferably more. Valve closure rates should be steady and reproducible, although this may be difficult to achieve if spring return valves or actuators are needed to ensure that valves fail safe to the closed position. A more uniform reduction of flow may be achieved by careful attention to valve port design or by the use of a valve actuator which gives a very sloe rate of closure over, the final 15% of the port closure. • Use a pressure relief system, surge tanks or similar devices to absorb the effects of the surge sufficiently quickly.

18. 參考資料庫: • 摘錄Oil Companies International Marine Forum. 及 International Chamber of Shipping 所出刊之International Safety Guide for Oil Tankers & Terminals資料。

19. 討論: § 業精於勤而荒於嬉 § ---End---

20. Question • 1.試分別依H/M保險及P&I保險觀點，Bunker Dispute (off spec bunkers)對owners的影響及其因應之道。 • 2.為減少消弭管路中之pressure surge，關閉閥門時應儘量平緩。請詳盡介紹可配用之設備，諸如pressure relief system及surge tanks。